[Margaret Pilkington]

I was growing up in the 1950's....I cannot recall Robinsons Fever Cure....I can remember Fennings Fever cure, but never had it...so I would not know what it looked like or what it tasted like.

I can remember Bile Beans,Fennings Cooling powders, Fennings Little Lung Healers, Scotts Emulsion, Indian Brandee(nothing at all like Brandy)Dr Collis Brownes Cholodyne, Carters Little Liver Pills, worm cakes...but not Robinsons Fever Cure.
Could you perhaps have got the name wrong?
The only thick brown gloopy stuff that was ever given to us was sulphur and treacle(nasty stuff) to purify the blood.
I know this does not answer your question,there may be others a bit older than me who have the answer